1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particular to an IPS (In Plane Switching)-method liquid crystal display device.
2. Background Art
As such a liquid crystal display device, there has been known a liquid crystal display device having the following constitution. Out of a pair of substrates which are arranged to face each other with liquid crystal sandwiched therebetween, in a pixel region formed on a liquid-crystal-side surface of one substrate, a first electrode having a planar shape formed of a transparent conductive film and linear second electrodes formed of a plurality of transparent conductive films are formed. Here, the first electrode is formed on the whole pixel region, and the linear second electrodes are formed in parallel to each other on an upper surface of an insulation film which is formed so as to also cover the first electrode in a state that the linear second electrodes overlap with the first electrode.
Molecules of the liquid crystal are driven by an electric field containing components parallel to the substrate between the first electrode and the second electrode and hence, the IPS-method liquid crystal display device is excellent in a so-called wide viewing angle. Further, both of these electrodes are formed of a transparent conductive film and hence, the IPS-method liquid crystal display device also exhibits an excellent numerical aperture.
Such a liquid crystal display device is usually driven by a so-called active matrix method in general. That is, the liquid crystal display device defines a region surrounded by a pair of neighboring gate signal lines and a pair of neighboring drain signal lines as a pixel region, and includes, in the pixel region, a thin film transistor which is turned on in response to a signal from the gate signal line, a pixel electrode to which a signal from the drain signal line is supplied via the turned-on thin film transistor, and a counter electrode which generates an electric field for driving liquid crystal between the pixel electrode and the counter electrode.
With respect to a liquid crystal display device having such constitution, there has been known a liquid crystal display device in which the first electrode functions as the pixel electrode and the second electrode functions as the counter electrode or a liquid crystal display device in which the first electrode functions as the counter electrode and the second electrode functions as the pixel electrode.
Such a liquid crystal display device is disclosed in WO01/018597 (patent document 1), for example.